Assessment of density functional theory methods on atomic and electronic structure of <i>β</i> -NiOOH structural models

A reliable determination of the atomic and electronic structure of nickel (oxy)hydroxide (NiOOH) is crucial for understanding its application as an oxygen evolution reaction (OER) electrocatalyst. However, discrepancies across experimental and computational studies have left the structure-composition-activity relationship of β-NiOOH poorly defined. In this work, we reassess the atomic and electronic structure of β-NiOOH using first-principles density functional theory calculations, emphasizing the influence of exchange-correlation functional and choice of ground-state structure on predicted structural and electronic properties. Simulated Raman is employed as an additional validation metric to inform structural assignments. Building on the optimized bulk β-NiOOH model, we construct and analyze a Fe-doped β-NiFeOOH (001) surface to explore the electronic and catalytic consequences of 25% Fe incorporation. Our comparative computational framework enables consistent evaluation of bulk and surface properties, offering deeper insights into the role of structural motifs in governing OER activity and guiding the design of improved earth-abundant electrocatalysts.